Liquid suction device

ABSTRACT

A liquid suction device used to suction a liquid contained in a well of a microchip which includes the well and a microchannel in fluid communication with the well. The liquid suction device includes: a suction nozzle having a tip opening at a tip thereof and being connected to piping at a rear end thereof, the suction nozzle suctioning the liquid through the tip opening; a pump connected to the piping, the pump supplying a suction pressure to the suction nozzle; and a driving unit for moving the suction nozzle relative to the well. In liquid suction device, the suction nozzle is moved by the driving unit until the tip opening contacts a bottom surface of the well while the suction nozzle applies a suction force produced by the suction pressure, thereby enabling suction of the liquid from the well and/or the microchannel.

TECHNICAL FIELD

The present invention relates to a liquid suction device which suctionsa liquid with a suction nozzle, and in particular to a liquid suctiondevice which suctions a liquid contained in wells of a microchip.

BACKGROUND ART

Enzyme immunological analyzers, which use a microplate having aplurality of liquid receptacles, which serve as reaction wells where asample and/or a reagent are reacted, have conventionally been known.Theses apparatuses generally includes a dispensing unit for dispensing asample and a reagent, a shaking unit and a temperature controller unitfor promoting the reaction, a cleaning unit for cleaning the liquidreceptacles, etc., and these units are separately operated by theoperator. In the cleaning unit, among these units, however, when arinsing liquid remaining in the liquid receptacles is suctioned with asuction nozzle, the rinsing liquid may still remain at the edge portionsof the bottom surfaces of the liquid receptacles, and the remainingrinsing liquid may vary the measurement results of the enzymeimmunoreaction.

Therefore, a method has been disclosed, in which the suction nozzle ispositioned at the center of each liquid receptacle, and the rinsingliquid is suctioned with moving the suction nozzle downward. Then, thesuction nozzle is moved to the edge portion of the bottom surface of theliquid receptacle to further suction the rinsing liquid, therebysuctioning the rinsing liquid remaining at the edge portion of thebottom surface (Japanese Unexamined Patent Publication No. 8(1996)-297125).

On the other hand, in recent years, in the fields of chemicals, optics,clinical technology, biotechnology, etc., clinical analysis apparatuseshave been developed, which use a microchip including a micro-sizedcircuit (so-called microchannels) formed on a substrate using amicromachining technology, which is commonly used for semiconductors,etc. The microchip includes wells serving as liquid receptacles, whichare in fluid communication with the microchannels. The microchip isused, for example, as a biochip which allows efficient microanalysis ofa biological material, such as DNA, in cooperation with anelectrophoresis analysis system. On the microchip, a series of analysisprocess steps, such as extraction of a component to be analyzed from thebiological material (an extraction step), analysis of the component tobe analyzed using a chemical/biochemical reaction (an analysis step),separation (a separation step) and detection (a detection step), areintegrated. This integrated system is also called as μ-TAS (micro-TAS),Lab-on-a-Chip, etc.

In the above-described liquid suction method, however, the suctionnozzle is moved down to the center portion of the liquid receptacle tosuction the liquid, and then is further moved to the edge portion tosuction the liquid, in order to reliably suction the liquid remaining atthe edge portion of the bottom surface of the liquid receptacle.Therefore, it is necessary to move the suction nozzle in at least twodirections, and this is not an efficient way for suctioning a slightamount of liquid.

DISCLOSURE OF THE INVENTION

In view of the above-described circumstances, the present invention isdirected to providing a liquid suction device which efficiently suctionsa liquid remaining in liquid receptacles, in particular, at edgeportions of bottom surfaces of wells of a microchip.

The liquid suction device of the invention is a liquid suction devicefor suctioning a liquid contained in a well of a microchip, themicrochip including the well for containing the liquid and amicrochannel in fluid communication with the well, the liquid suctiondevice including: a suction nozzle having a tip opening at a tip thereofand being connected to piping at a rear end thereof, the suction nozzlesuctioning the liquid through the tip opening; a pump means connected tothe piping, the pump means supplying a suction pressure to the suctionnozzle; and a moving means for moving the suction nozzle relative to thewell, wherein the suction nozzle is moved by the moving means until thetip opening contacts a bottom surface of the well while the suctionnozzle applies a suction force produced by the suction pressure, therebyenabling suction of the liquid from the well and/or the microchannel.

In the liquid suction device of the invention, it is preferred that,after the suction nozzle has contacted the bottom surface of the well,the moving means causes relative movement of the suction nozzle in adirection away from the bottom surface of the well while the suctionnozzle applies the suction force.

In the liquid suction device of the invention, the tip opening ispreferably formed to be parallel to the bottom surface of the well.

The liquid suction device of the invention may further include acushioning mechanism for cushioning the contact between the tip openingof the suction nozzle and the bottom surface of the well when thesuction nozzle is moved down.

In the liquid suction device of the invention, the cushioning mechanismis preferably formed by an elastic member.

According to the liquid suction device of the invention, the suctionnozzle is moved by the moving means until the tip opening contacts thebottom surface of the well while the suction nozzle applies the suctionforce produced by the suction pressure supplied by the pump means.Therefore, as the tip opening approaches the bottom surface of the well,the distance between the tip opening, which suctions the liquid, and theliquid remaining in the well decreases, and the flow rate in the liquidremaining in the well increases. In this manner, even if the liquidcontained in the well has a high viscosity, for example, and the liquidF adheres to the circumferential surface, in particular the edgeportion, of the well and remains there due to the surface tension, etc.,of the liquid, the remaining liquid can more easily be suctioned sincethe adhered liquid can be more easily separated due to the increasedflow rate in the remaining liquid F. Therefore, the amount of the liquidremaining in the well can be reduced.

Further, in the aspect of the liquid suction device of the invention inwhich the moving means causes relative movement of the suction nozzle ina direction away from the bottom surface of the well while the suctionnozzle applies the suction force after the suction nozzle has contactedthe bottom surface of the well, the suction nozzle is moved away fromthe bottom surface of the well after the tip opening has contacted thebottom surface of the well to be substantially sealed by the bottomsurface and a negative pressure has been generated inside the suctionnozzle. Therefore, when the suction nozzle is moved away from the bottomsurface of the well, the negative pressure generates a suction force.Since the suction nozzle is still applying the suction force at thistime, the suction force applied by the suction nozzle includes both thesuction force provided by the pump and the suction force provided by thenegative pressure. Thus, the suction force applied by the suction nozzlecan be increased. Therefore, even if the liquid still remains at theedge portion of the well, the liquid F can be suctioned with a strongersuction force.

As described above, the liquid remaining at the bottom edge portion ofthe well can efficiently be suctioned only by moving the suction nozzle,which applies the suction force, in one direction, i.e., in the verticaldirection. In this manner, such a situation that the liquid remaining atthe edge portions of the bottom surfaces of the wells of the microchipis introduced into the microchannels during a microanalysis operationcan be prevented, thereby preventing contamination and improvingaccuracy of the microanalysis.

Further, in the aspect of the liquid suction device of the invention inwhich the tip opening of the suction nozzle is formed to be parallel tothe bottom surface of the well, a larger contact area can be providedwhen the tip opening contacts the bottom, and this enhances the sealingproperty. Further, when the tip opening approaches the bottom surface ofthe well, the distance between the tip opening and the bottom surface ofthe well is the same at any portion of the edge of the tip opening.Therefore, the flow rate in the remaining liquid F can be made uniformand the liquid F can be evenly suctioned.

Further, in the aspect of the liquid suction device of the inventionfurther including a cushioning mechanism for cushioning the contactbetween the tip opening of the suction nozzle and the bottom surface ofthe well when the suction nozzle is moved down, the cushioning mechanismcan prevent the tip of the suction nozzle from being further moved downby the moving means and pressed against the bottom of the well, therebypreventing damage, etc., of the suction nozzle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating the configuration of a liquid suctiondevice according to the present embodiment,

FIG. 2 is a diagram for explaining how a liquid contained in a well issuctioned by the liquid suction device of the present embodiment,

FIG. 3 shows perspective views and a sectional view of a microchip,

FIG. 4 is a diagram for explaining how the liquid remaining at a wellbottom portion is suctioned by the liquid suction device of the presentembodiment,

FIG. 5 is a diagram illustrating the structure of a cushioningmechanism,

FIG. 6 is a diagram illustrating operation of a suction nozzle, and

FIG. 7 is a diagram illustrating the configuration of a liquid suctiondevice according to another embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereafter, one embodiment of a liquid suction device 1 according to thepresent invention is described in detail with reference to the drawings.FIG. 1 shows the configuration of the liquid suction device 1 of thisembodiment. It should be noted that the direction in which a tip opening2 a of a suction nozzle 2 of the liquid suction device 1 of thisembodiment faces is referred to as “downward” (downward in the drawing),for convenience.

The liquid suction device 1 of this embodiment is incorporated into aclinical analysis apparatus, such as a biochemical analyzer, used at amedical institution, a research institute, etc. The liquid suctiondevice 1 is used to suction a liquid, such as a sample, a reagent or arinsing liquid, which is contained in containers, such as test tubes ora plurality of wells, which serve as liquid receptacles, formed in amicrochip. The liquid suction device 1 is mainly used to suction aliquid, such as a rinsing liquid (for example, water) remaining in thecontainers during a step of cleaning the containers, which does notrequire accuracy of the amount of liquid to be suctioned.

As shown in FIG. 1, the liquid suction device 1 generally includes: thesuction nozzle 2; a nozzle driving unit 33, serving as a moving means 3,which includes a vertical movement mechanism unit 31 for moving thesuction nozzle 2 in the vertical direction (the depth direction of areceptacle (or container) 8) and a horizontal movement mechanism unit 32for moving the suction nozzle 2 in the horizontal direction; a suctionpump 41 and a pump driving unit 42, serving as a pump means 4, whichsupply a suction pressure to the suction nozzle 2; a controller unit 5which controls the nozzle driving unit 33 and the pump driving unit 42;a waste liquid tank 6 which stores a liquid F suctioned by the suctionnozzle 2; and piping 7 which connects between the suction nozzle 2 andthe waste liquid tank 6.

The suction nozzle 2 is substantially cylindrical, and includes the tipopening 2 a, through which the liquid F is suctioned. The suction nozzle2 is disposed with the tip opening 2 a facing down so as to be movablein the vertical and horizontal directions by the vertical movementmechanism unit 31 and the horizontal movement mechanism unit 32. Thevertical movement mechanism unit 31 and the horizontal movementmechanism unit 32 are formed, for example, by a transport mechanism suchas a power transmission mechanism using a pulley or a ball screwmechanism, and drive control of these mechanisms is achieved by a motor,etc., provided in the nozzle driving unit 33. The suction nozzle 2 ismoved by the controller unit 5, which is described later, so that thereceptacle 8 containing the liquid F is positioned below the tip opening2 a of the suction nozzle 2.

It should be noted that, on the tip opening 2 a of the suction nozzle 2,a tip in the form of a pipette, which can be replaced depending on thetype of the liquid F, may be attached. Although the suction nozzle 2 ofthe liquid suction device 1 of this embodiment can be moved above thereceptacle 8 by the nozzle driving unit 33, this is not intended tolimit the liquid suction device of the invention. The nozzle drivingunit 33 may not include the horizontal movement mechanism unit 32, andthe receptacle 8, for example, may be provided with a moving means thatcan move the receptacle 8 below the suction nozzle 2. That is, itsuffices that the relative movement between the suction nozzle 2 and thereceptacle 8 can be achieved.

One end of the piping 7 is connected to the upper portion of the suctionnozzle 2, and the other end of the piping 7 is connected via the suctionpump 41 to the substantially cylindrical waste liquid tank 6 having theopen upper end. Although the waste liquid tank 6 of this embodiment isformed by a substantially cylindrical container with the open upper end,this is not intended to limit the invention. The waste liquid tank 6 mayhave any shape, such as a rectangular cylinder or a spherical container,as long as it can store the liquid F, and the shape of the waste liquidtank 6 may be changed as appropriate.

The suction pump 41 supplies a suction pressure to the suction nozzle 2,and drive control of the suction pump 41 is achieved by the pump drivingunit 42 provided with a motor, etc. The suction pump 41 uses the liquidF as a pressure medium. The suction pump 41 may be formed by any ofvarious types of pumps, such as a centrifugal pump, an axial flow pump,a reciprocating pump or a rotary pump, and the type of the pump may bechanged as appropriate.

The controller unit 5 is provided with data about the position and theshape of the receptacle 8, data about the suction pressure of thesuction pump 41, and data about the diameter of the piping 7, andcontrols the nozzle driving unit 33 and the pump driving unit 42 basedon these data. These data may be changeable by the user, as necessary.The data about the shape of the receptacle 8 includes data about amaximum sectional area S of the interior of the receptacle 8 along aplane parallel to the liquid level of the liquid F contained in thereceptacle 8, i.e., in the horizontal direction. In the invention, theinterior of the receptacle refers to a space in the receptacle in whichthe liquid can be held.

FIG. 2( a) is a perspective view of a microchip 8′ provided with thewells 8 serving as the receptacles in this embodiment, FIG. 2( b) is aperspective view of the microchip 8′ of FIG. 2( a) viewed from below,FIG. 2( c) is a sectional view of the wells 8 of FIG. 2( a), and FIG. 3is a diagram for explaining how the liquid F in the wells 8 is suctionedby the liquid suction device 1 of the invention. It should be noted thatthe side of the microchip 8′ of this embodiment provided with openings 8a of the wells 8 (the upper side in each drawing) is referred to as theupper side, for convenience.

The receptacles 8 of this embodiment are liquid receptacles formed inthe microchip 8′, and are generally called wells. As shown in FIG. 2(a), the microchip 8′ has a substantially rectangular shape or anarrow-like shape and is formed of a synthetic resin. The microchip 8′includes the plurality of wells 8 formed on an upper surface 8A thereof.As shown in FIG. 2( b), a glass plate (a transparent plate member) 81 isattached at a lower surface 8B of the microchip 8′. As shown in FIG. 3(c), the glass plate 81 is formed by a first substrate 82 and a secondsubstrate 83 bonded to the upper surface of the substrate 82. The firstsubstrate 82 includes microchannels 82 a formed in the upper surfacethereof, and the second substrate 83 includes through holes 83 a (wellbottom portion 83 a), which are in fluid communication with themicrochannels 82 a and form the bottom portions of the wells.

Each well 8 includes the opening 8 a at the upper end thereof, and awell taper portion 8 b, which extends downward from the opening 8 a tojoin to the well bottom portion 83 a. The well taper portion 8 b isformed such that the diameter thereof gradually decreases from the upperend to the lower end. Since the well bottom portion 83 a has an evensmaller diameter, the maximum sectional area S of the well 8 is equal tothe area at the upper end opening 8 a, and an annular step portion 8 cis formed at the boundary between the well taper portion 8 b and thewell bottom portion 83 a. The first substrate 81 and the secondsubstrate 82 may be formed of a synthetic resin, besides glass, and bothof them may be transparent, or only one of them, through which opticalmeasurement is carried out, may be transparent. Although themicrochannels 82 a are formed in the first substrate 82 in thisembodiment, this is not intended to limit the microchip used with theliquid suction device of the invention. The microchannels 82 a may beformed in the second substrate 83, as long as the microchannels 82 a areformed between the first substrate 82 and the second substrate 83.

The liquid F contained in the wells 8 of microchip 8′ having theabove-described structure is suctioned by the liquid suction device 1described above. As a anterior step in a suction operation, the suctionnozzle 2 is moved down to suction the liquid F such that the liquid Fdoes not adhere to the outer surface of the nozzle 2. Then, as aposterior step, the nozzle 2 is further moved down until the tip opening2 a of the suction nozzle 2 contacts the bottom surface of the wellbottom portion 83 a. First, the anterior step is described in detail.

The suction nozzle 2 of the liquid suction device 1 is moved in thedepth direction (downward) at a constant traveling speed V by the nozzledriving unit 33, and suctions the liquid F with a suction force, whichis generated in the suction nozzle 2 by a suction pressure supplied fromthe suction pump 41, before the suction nozzle 2 contacts the liquid F,i.e., at a suction rate Q per unit time, which satisfies Q>S×V. That is,the suction nozzle 2 is moved down by the nozzle driving unit 33 at theconstant traveling speed V from the position in which the tip opening 2a is positioned above the well 8 (see the arrows in FIG. 3). Before thesuction nozzle 2 contacts the liquid F, the suction pressure has alreadybeen supplied to the suction nozzle 2 from the suction pump 41, and thesuction rate per unit time, which is achieved by the suction forcegenerated in the suction nozzle 2 by the suction pressure, has alreadysatisfied Q>S×V. The suction rate Q per unit time herein refers to avolume of the liquid F which can be suctioned by the suction nozzle 2per unit time. The suction pressure has been supplied by the suctionpump 41 before the downward movement of the suction nozzle 2 is started.In this manner, the suction nozzle 2 can start the suction of the liquidF with the stable suction rate Q, without being influenced by loweringof the suction rate Q due to the shape of the piping 7, characteristicsof the start-up time of the pump means 4, etc.

In the liquid suction device 1 of this embodiment, the suction nozzle 2suctions the liquid F before the suction nozzle 2 contacts the liquid F,however, this is not intended to limit the liquid suction device of theinvention. The suction nozzle 2 may suction the liquid F as soon as thesuction nozzle 2 contacts the liquid F, as long as the liquid F does notadhere to the outer surface of the suction nozzle 2. Although the pumpdriving unit 42 is controlled by the controller unit 5 in the liquidsuction device 1 of this embodiment, this is not intended to limit theinvention. Manual control may be used as long as the suction pressurecan be supplied to the suction nozzle 2 before or as soon as the suctionnozzle 2 contacts the liquid F.

As described above, the suction nozzle 2 is moved down with the suctionrate Q per unit time is ensured. Therefore, the suction nozzle 2suctions air A while being moved down. The suction nozzle 2 suctioningthe air A continues to be moved down toward the liquid level of theliquid F, and suctions the liquid F in the well 8 when the suctionnozzle 2 reaches a predetermined position above the liquid level, asshown in FIG. 3( a). Since the liquid suction device 1 of thisembodiment is used in a cleaning step of the wells 8, etc., which doesnot require accuracy of the suction rate of the liquid F, there is noproblem in suctioning the air A. While the suction nozzle 2 suctions theliquid F and/or the air A at the suction rate Q per unit time, thesuction nozzle 2 is further moved down at the constant traveling speedV.

Since the inner circumferential surface of the well taper portion 8 b istapered, the interior volume of the well 8 across which the tip opening2 a of the suction nozzle 2 is moved per unit time is always differentdepending on the position of the tip opening 2 a of the suction nozzle 2in the depth direction. Since it suffices that the suction rate Q perunit time of the liquid suction device 1 is larger than the interiorvolume of the well 8 across which the tip opening 2 a of the suctionnozzle 2 is moved per unit time, a hypothetical volume S×V, which islarger than the interior volume of the well 8 across which the tipopening 2 a of the suction nozzle 2 is actually moved, is calculatedfrom the maximum sectional area S of the well 8 and the traveling speedV of the suction nozzle 2, to set the suction rate Q which is largerthan the hypothetical volume S×V (see FIG. 3( b)).

Since the suction rate Q, i.e., the volume of the liquid F and the air Asuctioned by the suction nozzle 2 per unit time, is set to be largerthan the hypothetical volume S×V, the tip opening 2 a of the suctionnozzle 2 is always positioned above the liquid level and the suctionnozzle 2 does not contact the liquid F. Thus, the liquid F does notadhere to the outer surface of the suction nozzle 2, and the outersurface of the suction nozzle 2 of the liquid suction device 1 of thisembodiment can be prevented from being contaminated. In this manner,adhesion of the liquid to the outer surface of the suction nozzle 2 canbe prevented without providing a complicated control mechanism whichincludes, for example, a liquid level detection mechanism, etc., andthis saves space as well as cost for providing such a mechanism. In theliquid suction device 1 of this embodiment, in order to satisfy Q>S×V,the value of the traveling speed V may be varied or the value of thesuction rate Q may be varied. These can be changed as appropriate.

Next, the posterior step is described in detail. While the suctionnozzle 2 suctions the liquid F, the suction nozzle 2 is further moveddown by the nozzle driving unit 33 from the position shown in FIG. 3( b)toward the well bottom portion 83 a. At this time, all the liquid F inthe well 8 including the liquid F at the well bottom portion 83 a mayhave been suctioned by the suction nozzle 2, or the liquid F may remainat the well bottom portion 83 a (see FIG. 4( a)). That is, it sufficesthat the suction nozzle 2 applies the suction force provided by thesuction pressure supplied from the pump 41, and the suction nozzle 2may, for example, suction only the air A without suctioning the liquidF. The characteristic feature of the invention is that the suctionnozzle 2 is moved down with applying the suction force until the tipopening 2 a of the suction nozzle 2 contacts the bottom surface of thewell bottom portion 83 a. FIG. 4 is a diagram for explaining how theliquid F remaining at the well bottom portion 83 a is suctioned by theliquid suction device 1 of this embodiment.

As the suction nozzle 2 is moved down with applying the suction force,as described above, the tip opening 2 a is positioned in the well bottomportion 83 a, as shown in FIG. 4( a). At this time, the suction nozzle 2is moved down with suctioning the liquid F if the liquid F still remainsat the well bottom portion 83 a. Then, the suction nozzle is furthermoved down in the similar manner, as shown in FIG. 4( b). As the tipopening 2 a of the suction nozzle 2 approaches the bottom surface of thewell bottom portion 83 a, the distance between the tip opening 2 a, fromwhich the suction force is applied, and the liquid F remaining at thewell bottom portion 83 a decreases, and the flow rate in the liquid Fremaining at the well bottom portion 83 a (indicated by the arrow shownin the liquid at the well bottom portion in the drawing) increases.

In this manner, even if the liquid F contained in the well 8 has a highviscosity, for example, and the liquid F adheres to the circumferentialsurface, in particular the edge portion, of the well bottom portion 83 aand remains there due to the surface tension of the liquid F, theremaining liquid F can more easily be suctioned since the adhered liquidF can be more easily separated due to the increased flow rate in theremaining liquid F. Thus, the amount of the liquid F remaining at thewell bottom portion 83 a can be reduced. The tip opening 2 a may bemoved down toward the substantial center of the well bottom portion 83a, or may be moved down toward the edge portion of the well bottomportion 83 a. This can be changed as appropriate. As shown in FIG. 5,the tip opening 2 a may be moved down along the edge portion of thebottom surface of the well bottom portion 83 a. This allows reliablesuction of the liquid F remaining at the edge portion of the bottomsurface of the well bottom portion 83 a.

Then, as shown in FIG. 4( c), the suction nozzle 2 is further moved downwith applying the suction force, until the tip opening 2 a contacts thebottom surface of the well 8, i.e., the bottom surface of the wellbottom portion 83 a. Then, the tip opening 2 a of the suction nozzle 2abuts on the bottom surface of the well bottom portion 83 a, and the tipopening 2 a is substantially sealed by the bottom surface of the wellbottom portion 83 a. In this state, a negative pressure is generatedinside the suction nozzle 2. The tip opening 2 a of the suction nozzle 2of this embodiment is formed to be parallel to the bottom surface of thewell bottom portion 83 a to enhance the sealing property. Further, whenthe tip opening 2 a approaches the bottom surface of the well bottomportion 83 a, as described above, the distance between the tip opening 2a and the bottom surface of the well bottom portion 83 a is the same atany portion of the edge of the tip opening 2 a. Therefore, the flow ratecan be made uniform at the entire edge of the tip opening 2 a and theliquid F can be evenly suctioned. The tip opening 2 a may have an unevenshape or a saw-like shape, as long as the sealing property is notexcessively lowered.

Since the liquid suction device of the invention is used to suction theliquid F contained in the wells 8 of the microchip 8′, which includesthe microchannels 82 a in fluid communication with the wells 8, aclearance, through which the air and/or the liquid can flow in from orflow out to the microchannel 82 a, is formed between each tip opening 2a and the bottom surface of each well bottom portion 83 a, as shown inFIG. 4( c). The clearance can prevent generation of an excessivenegative pressure inside the suction nozzle 2, which may otherwise leadto damage of the suction nozzle 2, the motor of the nozzle driving unit33, etc. Further, this facilitates suction of the air and/or the liquidfrom the microchannels 82 a.

Then, as shown in FIG. 4( d), the suction nozzle 2 is moved up from thesubstantially sealed state, with applying the suction force, in thedirection in which the tip opening 2 a is moved away from the bottomsurface of the well bottom portion 83 a. Since the negative pressure isgenerated inside the suction nozzle 2, the liquid and/or the air flowinto the suction nozzle 2 through between the tip opening 2 a and thebottom surface of the well bottom portion 83 a. Since the suction nozzle2 is still applying the suction force at this time, the suction forceapplied by the suction nozzle 2 includes both the suction force providedby the pump 41 and a suction force generated by the negative pressure.Thus, the suction force applied by the suction nozzle 2 can beincreased. Therefore, even if the liquid F still remains at the edgeportion of the well bottom portion 83 a, the liquid F can be suctionedwith a stronger suction force.

As described above, according to the liquid suction device 1 of thisembodiment, the liquid F remaining at the edge portion of the bottomsurface of the well 8, i.e., the well bottom portion 83 a, canefficiently be suctioned only by moving the suction nozzle 2 in onedirection i.e., in the vertical direction, by the nozzle driving unit 33while the suction nozzle 2 applies the suction force. In this manner,such a situation that the liquid F remaining at the edge portions of thebottom surfaces of the well bottom portions 83 a of the microchip 8′ isintroduced into the microchannels 82 a during a microanalysis operationcan be prevented, thereby preventing contamination and improvingaccuracy of the microanalysis. In addition, the residual liquid in themicrochannels 82 a can be suctioned, thereby preventing contamination.

Examples of the liquid F in this embodiment may include an analyticalreagent, a test sample, a rinsing liquid, cleaning water, etc.

In the liquid analysis device 1 of this embodiment, an outer diameter D1of the suction nozzle is preferably in the range from 0.5 to 1.2 mm. Adiameter D2 of the well bottom portion is preferably in the range from1.2 mm to 2.2 mm. Further, the relationship between the outer diameterD1 of the suction nozzle and the diameter D2 of the well bottom portionis preferably: (D2−D1)/2<0.6 mm (see FIG. 4( a) for the referencesymbols).

Next, a second embodiment of the liquid suction device according to theinvention is described. The liquid suction device of this embodimentincludes a cushioning mechanism 20 in addition to the components of theliquid suction device 1 of the above-described embodiment, and thereforeonly the cushioning mechanism 20 is explained. FIG. 6 shows thestructure of the cushioning mechanism 20.

As shown in FIG. 6, the cushioning mechanism 20 of this embodimentincludes: a support member 21 which fixes and supports the rear end ofthe suction nozzle 2; a fixing member 22 being fixed to the verticalmovement mechanism unit 31 and the horizontal movement mechanism unit 32(not shown) to be moved in conjunction with the mechanism units 31 and32; and a spring member 23 serving as an elastic member, with the upperend thereof engaging with the support member 21 and the lower endthereof engaging with the fixing member 22.

When the suction nozzle 2 is moved down and the tip opening 2 a of thenozzle 2 contacts the bottom surface of the well bottom portion 83 a, asdescribed above, and if, for example, the suction nozzle 2 is moved downexcessively by the nozzle driving unit 33, the repulsive force of thespring member 23 of the cushioning mechanism 20 moves the suction nozzle2 relatively upward via the support member 21. Thus, the contact betweenthe tip opening 2 a of the suction nozzle 2 and the bottom surface ofthe well bottom portion 83 a can be cushioned, thereby preventing damageof the suction nozzle 2, lowering of accuracy of the nozzle driving unit33, etc. It should be noted that the cushioning mechanism 20 mayalternatively be provided on the well 8 side.

Although the liquid suction device 1 of the above-described twoembodiments uses the liquid F as the pressure medium for suctioning theliquid F, this is not intended to limit the invention. The air A may beused as the pressure medium. FIG. 7 shows the configuration of a liquidsuction device 1′ of a third embodiment. Components of the liquidsuction device 1′ which are the same as those of the above-describedliquid suction device 1 are designated by the same reference numeralsand explanations thereof are omitted.

As shown in FIG. 7, the liquid suction device 1′ of this embodimentincludes: the suction nozzle 2; the nozzle driving unit 33, serving asthe moving means, which includes the vertical movement mechanism unit 31for moving the suction nozzle 2 in the vertical direction (the depthdirection of the receptacle 8) and the horizontal movement mechanismunit 32 for moving the suction nozzle 2 in the horizontal direction; anegative pressure pump 91, which serves as a pump means 9 for supplyinga suction pressure to the suction nozzle 2, a negative pressure chamber92, a pump driving unit 93 and a second piping 71 connecting thesecomponents; the controller unit 5 which controls the nozzle driving unit33 and the pump driving unit 93; the waste liquid tank 6 which stores aliquid F suctioned by the suction nozzle 2; the piping 7 which connectsbetween the suction nozzle 2 and the negative pressure chamber 92; athird piping 72 which connects between the negative pressure chamber 92to the waste liquid tank 6; an opening and closing valve 94 disposed atthe piping 7; and a pump 95 connected to the third piping 72.

The other end of the piping 7, which has the one end connected to thesuction nozzle 2, is inserted into the negative pressure chamber 92 viathe opening and closing valve 94. The negative pressure chamber 92 has aspace R therein, which contains the gas A (air A) and is sealed. One endof the second piping 71 is connected to the negative pressure chamber 92in fluid communication with the space R. The second piping 71 includesat the other end thereof an opening 71 a, which is in fluidcommunication with the ambient air, and the negative pressure pump 91 isconnected to the middle of the second piping 71. Driving of the negativepressure pump 91 is controlled by the pump driving unit 93 including amotor, etc. The negative pressure pump 91 suctions the air A in thespace R and discharges the air A through the opening 71 a to generate anegative pressure in the space R. The negative pressure generated in thespace R serves as the suction pressure supplied to the suction nozzle 2,and the suction pressure provides the suction force of the suctionnozzle 2. At this time, the suction rate per unit time of the suctionnozzle 2 satisfies Q>S×V, similarly to the above-described embodiment.Then, the suction nozzle 2 is moved down with applying the suction forceuntil the suction nozzle 2 contacts the bottom surface of the wellbottom portion 83 a, similarly to the above-described embodiment, andthe liquid F suctioned by the suction nozzle 2 is discharged into thenegative pressure chamber 92 through the piping 7. In order to preventthe vapor and/or droplets of the liquid F discharged into the negativepressure chamber from flowing out, a filter 96 is disposed between thenegative pressure pump 91 and the opening 71 a. Then, the liquid F inthe negative pressure chamber 92 is discharged to the waste liquid tank6 via the third piping 72 connected to the negative pressure chamber 92by the pump 95 connected to the third piping 72.

1-5. (canceled)
 6. A liquid suction device for suctioning a liquidcontained in a well of a microchip, the microchip including the well forcontaining the liquid and a microchannel in fluid communication with thewell, the liquid suction device comprising: a suction nozzle comprisinga tip opening at a tip thereof and being connected to piping at a rearend thereof, the suction nozzle suctioning the liquid through the tipopening; a pump means connected to the piping, the pump means supplyinga suction pressure to the suction nozzle; and a moving means for movingthe suction nozzle relative to the well, wherein the suction nozzle ismoved by the moving means until the tip opening contacts a bottomsurface of the well while the suction nozzle applies a suction forceproduced by the suction pressure, thereby enabling suction of the liquidfrom the well and/or the microchannel.
 7. A liquid suction device asclaimed in claim 6, wherein, after the suction nozzle has contacted thebottom surface of the well, the moving means causes relative movement ofthe suction nozzle in a direction away from the bottom surface of thewell while the suction nozzle applies the suction force.
 8. A liquidsuction device as claimed in claim 6, wherein the tip opening is formedto be parallel to the bottom surface of the well.
 9. A liquid suctiondevice as claimed in claim 7, wherein the tip opening is formed to beparallel to the bottom surface of the well.
 10. A liquid suction deviceas claimed in claim 6, further comprising a cushioning mechanism forcushioning the contact between the tip opening of the suction nozzle andthe bottom surface of the well when the suction nozzle is moved down.11. A liquid suction device as claimed in claim 7, further comprising acushioning mechanism for cushioning the contact between the tip openingof the suction nozzle and the bottom surface of the well when thesuction nozzle is moved down.
 12. A liquid suction device as claimed inclaim 8, further comprising a cushioning mechanism for cushioning thecontact between the tip opening of the suction nozzle and the bottomsurface of the well when the suction nozzle is moved down.
 13. A liquidsuction device as claimed in claim 9, further comprising a cushioningmechanism for cushioning the contact between the tip opening of thesuction nozzle and the bottom surface of the well when the suctionnozzle is moved down.
 14. A liquid suction device as claimed in claim10, wherein the cushioning mechanism comprises an elastic member.
 15. Aliquid suction device as claimed in claim 11, wherein the cushioningmechanism comprises an elastic member.
 16. A liquid suction device asclaimed in claim 12, wherein the cushioning mechanism comprises anelastic member.
 17. A liquid suction device as claimed in claim 13,wherein the cushioning mechanism comprises an elastic member.